That includes Microsoft founder Bill Gates, who retains his title as the richest man in the world, as well as Amazon's Jeff Bezos and Facebook's Mark Zuckerberg. Though US moguls dominate the world of tech billionaires, China's Jack Ma of Alibaba and Pony Ma of Tencent also earn spots in the top nine.

Tech money proves to be hard-earned as well: All nine of the richest billionaires are self-made, thanks to the powerful companies they built themselves, including Facebook, Microsoft, and Google.

For the ranking, Business Insider culled data from the Bloomberg Billionaires Index as of March 1, when the index relaunched in its expanded format. The index updates daily to provide up-to-the-minute data on the world's wealthiest men and women. You can read the full methodology here.

Below, read on to see the nine richest billionaires who made their fortunes in tech.

9. Ma Huateng

Software engineer Ma Huateng (aka Pony Ma) founded China's largest internet portal, Tencent Holdings, in 1998. He was 26. Ma's company has a number of successful and widely used platforms in its portfolio, including QQ, its instant-messaging service, which is one of the world's 10 largest websites; a mobile-texting service (WeChat) with over 800 million users; a mobile-commerce product (WeChat Wallet); and an online-gaming community (Tencent Games), the largest in China.

Ma's wealth has increased by $4.7 billion in the past year.

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8. Steve Ballmer

Steve Ballmer dropped out of business school at Stanford in 1980 to join Harvard friend Bill Gates at Microsoft as the company's first business manager, earning a $50,000 salary and a stake in the company. During his tenure, Ballmer held positions as vice president of marketing, vice president of systems software, and executive vice president of sales and support, and was often referred to as "the numbers guy."

He became CEO of the company in 2000 after Gates stepped down, and he remained in charge of the software giant until Satya Nadella replaced him in 2014. While running Microsoft, the company's revenue grew by 294% and profits by 181% — although its market share was surpassed by Google and Apple during the same period. Still, the early stake Ballmer acquired in the company made him immensely wealthy.

After stepping down as CEO, Ballmer fulfilled his dream of owning an NBA franchise, paying $2 billion in a deal to buy the Los Angeles Clippers, now his main venture.

Ballmer's net worth has increased $4.8 billion in the last year.

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7. Jack Ma

The richest person in China, Alibaba founder and executive chairman Jack Ma reportedly started China's first internet company in 1988: China Yellowpages. He lost control of that company to a state-owned telecom in 1996 and started Alibaba three years later with just $60,000. Fifteen years after its inception, the e-commerce company broke records with a $25 billion initial public offering— the world's largest ever.

Post-IPO, however, Alibaba's good fortune began to slip. The company's shares dropped 22% in 2015, most likely because of China's slowing economy and concerns over counterfeiters using the company's platform. Ma didn't worry, though. He acknowledged that 2016 would be a trying time for the Chinese economy, but remained confident in Alibaba's long-term success.

Ma's wealth has increased by $8.4 billion over the past year.

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6. Sergey Brin

Along with cofounder Larry Page, Sergey Brin helped facilitate Google's massive restructuring, which the company announced in 2015. The move put Google under the auspices of a holding company called Alphabet, run by Brin as president and Page as CEO. Google's other ventures, such as Nest and Google X, are separate companies also under the Alphabet umbrella.

The restructuring allowed Brin to focus on exploring inventive new "moonshot" projects and ideas. With top talent and an abundance of resources at its disposal, Alphabet has already made automated homes and self-driving cars a reality.

Brin, who emigrated from Moscow to the US as a child, connected with Page in 1995 at Stanford, where they were each pursuing a PhD. Three years later they founded Google, now one of the most powerful companies on the planet.

Over the past year, Brin's wealth has increased by $4.1 billion.

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5. Larry Page

As a Stanford PhD student in 1998, Larry Page teamed up with classmate Sergey Brin to create BackRub, an early search engine. The project eventually morphed into Google — now called Alphabet — one of the largest and farthest-reaching companies in the world, worth more than $581 billion. Over the past year, Page's personal net worth has increased by $4.3 billion.

Page oversaw major changes to Google's business structure in 2015, starting with the creation of Alphabet, the holding company that manages Google and all of its related ventures, including Nest, Calico, and Google X. Previously the chief executive of Google, Page moved up to helm Alphabet, which has its hands in everything from home automation to self-driving cars to prolonging human life.

Page doesn't make a lot of splashy purchases, but the alternative-energy advocate does own an eco-friendly mansion in Palo Alto that uses geothermal energy and rainwater capture. He's also an avid kiteboarder.

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4. Larry Ellison

In 1977, Larry Ellison teamed up with two colleagues from an electronics company to start their own programming firm, which landed a contract not long after to build a relational database-management system for the CIA under the project code Oracle. The project grew into what is known today as Oracle Corp., which produced $37 billion in revenue last year. In 2010, Ellison reduced his annual salary from $1 million to $1, but he still takes in more than $60 million in total compensation thanks to generous stock awards. Ellison stepped down as CEO in 2014 after 38 years on the job and took on the role of chief technology officer.

The tech tycoon is also a generous philanthropist through partnerships with wildlife conservation groups and the Lawrence Ellison Foundation, which supports organizations that research aging and global infectious diseases. He's also a member of Bill Gates and Warren Buffett's Giving Pledge, committing to give away at least half of his fortune.

In the last year, Ellison's wealth has increased by $5.2 billion.

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3. Mark Zuckerberg

In 2004, Mark Zuckerberg, then a 19-year-old sophomore at Harvard, launched TheFacebook.com, a rudimentary version of the now ubiquitous social network known as Facebook. Zuckerberg dropped out of college to work full-time as Facebook's CEO, and the site quickly exploded in popularity. Today, it attracts more than a billion users daily and is worth nearly $400 billion. At 32, Zuckerberg is by far the youngest of the 50 richest people in the world. His wealth has increased by $11.1 billion in the past year.

In December 2015, Zuckerberg and his wife, Priscilla Chan pledged give away 99% of their wealth in their lifetimes through an organization called the Chan Zuckerberg Initiative, though some critics noted the organization wasn't a nonprofit charity itself and found the announcement misleading.

But this isn't the couple's first foray into philanthropy. They donated $25 million in the fight against Ebola in 2015, and they gave $100 million worth of Facebook shares toward improving a New Jersey public-school system.

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2. Jeff Bezos

Jeff Bezos earned his massive fortune by introducing e-commerce to the world. After spending time in finance on Wall Street, Bezos founded Amazon.com in the garage of his Seattle home in 1994 and operated it exclusively as an online book retailer. The company went public three years later and has since grown to include everything from furniture to food to Amazon's own consumer-electronics products, generating $136 billion in revenue in 2016.

Bezos also has interests outside of Amazon, including investments in his privately owned space company Blue Origin, which successfully launched its first spacecraft in 2015, and The Washington Post, the newspaper he bought in 2013.

Bezos' wealth has increased by $21.9 billion in the last year.

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1. Bill Gates

At just 20, Bill Gates cofounded Microsoft with his childhood friend Paul Allen. Months before his 31st birthday, the company went public, making Gates a billionaire. He served as CEO of the software titan until 2000 and was its chairman and largest shareholder until 2014. Though he still sits on the company's board, Gates is no longer actively involved in Microsoft.

Gates is not only the richest man in the world — his net worth increased by $10.6 billion in the last year alone — but he's also the most generous. Since 1999, Gates and his wife have helmed the Bill & Melinda Gates Foundation, one of the most powerful charities in the world. The foundation — which controls an endowment of more than $40 billion— aims to lift millions of people out of poverty, with a heavy focus on eliminating HIV, malaria, and other infectious diseases. The couple is also working on a plan to bring mobile banking to the 2 billion adults who don't have a bank account.

He's also cofounder of the Giving Pledge, which he launched in 2010 with good friend and fellow billionaire Warren Buffett as a promise to donate 50% or more of their fortunes. The Giving Pledge now counts Mark Zuckerberg and Elon Musk among its 156 members.